ocfs2_dlm: Silence a failed convert

When the lockres is in migrate or recovery state, all convert requests
are denied with the appropriate error status that is handled on the
requester node. This patch silences the erroneous error message printed
on the master node.

Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>